In such powder sprayers--or sprayguns--as are employed for painting and lacquering work, and as utilise electrostatic charging of the powder, attempts have been made, with a view to increasing the charging degree of the powder, to realise as good a turbulence and blending of the air-powder mixture as possible in the charging channel or channels employed in the powder spraygun. One method of achieving this has been to make the configuration of the channel proper irregular, spiral or of differing cross-section, so that turbulence will thereby be created. Examples of such constructions are disclosed in Swedish Patent Applications Nos. 7206316-7 and 8007919-7.
Another prior art method of increasing the turbulence and improving the charging degree in a powder spraygun with friction charging entails that a helicoid rotational movement is imparted to the powder at the same time as the powder runs through the charging channel in the gun. One example of such a construction is described in U.S. Pat. Ser. No. 4,359,192.
In summing up the prior art technology, it might be said that, given favourable conditions, it may very well be enough to provide sufficient charging of the powder. However, if the powder is not of a uniform or homogeneous nature, but consists of mixtures of different powder varieties or qualities, the prior art constructions do not function satisfactorily. In addition, problems have arisen in certain cases, in that the powder has received an uneven charge, such that certain particles in the powder flow have been greatly charged while others have been but moderately charged or not charged at all.